Energy Rating

What Is It?

In the final analysis, the Energy Rating (ER) number is the bottom line for energy-conscious consumers as it is the indicator of thermal performance. The ER number is not a temperature rating. It is a scale rating comparative thermal performance based on three factors: 1) solar heat gains; 2) heat loss through frames, spacer and glass; and 3) air leakage heat losses. It is a rating solely of energy performance, regardless of how or with what materials the exterior door or was built. Skylights are not rated using an energy rating; they are rated for solar heat gain and heat loss only. Door and skylight energy performance standards are defined in the CSA A440.2 standard.

The Higher The ER The Better

The ER can be used as an indicator of the effect the exterior doors will have on an annual heating bill. A high ER (over 40) means that the door will add more heat than it loses during the heating season. A lower ER means that the door loses more heat than they gain during the heat season. The lower the number, the more heat is lost and the higher the heating costs..

Things to Remember

Most patio doors will have better ER numbers than exterior doors. The reason for this is because patio doors tend to have more glass area relative to frame area. This translated into more solar gains and less frame losses and a higher ER number.

Compare Apples to Apples

The ER system is based on a formula, which calculates a single ER number for a specified size. Because all evaluations are done the same way, it makes comparisons between different manufacturers much easier. The ratings given will be for a standard size and not a particular door size. It is essential to compare ER numbers within each category as the test size may vary from one category to another. This results in different ER numbers for different categories. For this reason, you cannot compare ER numbers across categories.